Method of rectifying petroleum oils



Oct. 25, 1932. c KEITH, JR 1,883,934

METHOD OF RECTIFYING PETROLEUM OILS FiledJuly 10, 1928 Patented Get. as, was

UNI-To sra'rss nsane PATENT OFFICE PERCY C. KEITH, JR., OF BERNARDSVILLE, NEW JERSEY, ASSIGNOR TO THE M. W. KELLOGG COMPANY, OF NEW YORK, N. 'Y., A CORPORATION OF DELAWARE METHOD OF RECTIFYING PETROLEUM OILS Application filed July 10,

This invention relates to a method for rectifying petroleum oils and more particularly a method for rectifying petroleum oils under vacuum and will be understood from the following description read in conjunction with the drawing in which:

Figure 1 is an elevation partially in section of a preferred form of apparatus; and

Figures 2 and 3 are vertical sections showing{in detail parts of Figure 1.

eferringspecifically to Fig. 1, the oil inlet pipe 1 controlled by the valve 2 dis charges into the tubular heater'3. The tubular heater consists of a series of tubes joined, end to end, by cross-over connections to form a continuous circuit. The tubular heater will be hereinafter referred to as a pipe still. The pipe still is surrounded by the refractory setting 4 whichmay be heated through port 5 by the burner 6. The pipe still discharges through the outlet pipe 7 which is preferably covered with thermal insulation 7a into the distributor 8. The drum 9 is surrounded by thermal insulation 9a and carries horizontal partitions 10 and 11 respectively above and below the distribu- 6 tor. 8. These partitions carry conventional liquid vapor contacting devices such as bellcaps and overflow pipes, not shown. Immediately below the partition 11 is located a steam distributor 12 to which steam may be admitted by a pipe 13 controlled by the valve 14. Any li uid accumulated in the bottom of drum 9 a ove the upper level of overflow pipe 15 maybe withdrawn'either continuously or periodically by means of a valve 16 and diverted to an accumulator through pipe 17. The vapors evolved in the drum are conducted away thru the pipe 18 covered by thermal insulation 18a, which pipe dischar es into the rectifying column 20. The recti ying column is equipped with a number of horizontal partitions 21 which carry va or distributors such as bell-caps and over ow pipes, not shown in Fig. 1; Provision is made for taking off intermediate cuts from the column by means of the pots 23, 24, 25, 26, and 27 which are supplied with steam for stripping by means respectively of the pipes 28, 29, 30, 31 and 32. The stripped cuts are 1928. Serial No. 291,607.

conducted away from the system through the pipes 33, 34, 35, 36 and 37. The column is provided in its uppermost portion with cooling coils 40 and 41. The cooling coil 41 may be supplied with Water through the pipe 42. The cooling coil 40 may be supplied with oil through the pipe 43, which, after passing through the cooling coil, is discharged into the pipe 1 by which it is conveyed into the pipe still. Provision is made no for taking liquid away from the base of the rectifying column 20 by means of the pipe 50 controlled by the valve 51. Vapors are conducted away from the top of the column 20 by means of the pipe 55 which in turn is so connected to the jet ejector 56. The ejector 56 is supplied with steam throughthe pipe 57 controlled by the valve 58. The discharge from the ejector passes into the pipe 60, and is thereby conducted to the barometric con- 70 densor 61 by which it is finally condensed and any uncondensed gases are discharged at atmospheric pressure. The barometric condensor is supplied with condensing water through the pipe 62 controlled by the valve 76 Referring specifically to Figure 2, the stripping pot 23 rests on the partition 21 and is entirely closed. Oil is drained into the pot from the horizontal partition immediately above by means of the pipe controlled by the valve 71. It will be understood that the valve handle enters the wall of the bubble tower through a stufling box which is not shown. The stripping pot carries a horizontal partition 72 which in turn carries bellcaps or liquid vapor contacting devices, of any suitable form, 73, an overflow pipe 74 for conducting any excessive liquid over that necessary to maintain a definite level, into the lower part of the pot from which it may be continuously diverted to storage by means of the pipe 33. Steam for stripping may be supplied through the pipe 28 controlled by the valve 28a terminating in the distributor 28b. Any steam admitted to the distributor I after passing upwardly through the bell-caps 7 3 and removing the lighter vapors from the liquid on the plate 72, will be delivered through the pipe 76 into the space above the next higher horizontal partition;

The method of operating the apparatus is substantially as follows:

A petroleum oil to be distilled is passed through the pipe 43, coil 40 and pipe 1 into the ipe still 3. Any petroleum oil may be emp oyed for this purpose although the apparatus is particularly adapted to an oil containing constituents which should be distilled under vacuum to avoid cracking and which it is preferably desired to resolve into a number'of cuts by rectification. A suitable oil for this purpose is a crude oil or a residuum containing lubricating constituents. The oil is heated to complete or partial vaporization in the pipe still 3 and is led through the pipe 7 and distributor 8 into the drum 9. The vaporized hydrocarbons separate in the drum 9 while the unvaporized residuum flows through the partition 11 and then downwardly into the base of the drum from which it is periodically or continuously withdrawn by means of the pipes 15 and 17. Steam,

preferably super-heated, is admitted through the distributor 12 to strip the li hter components from the residuum and to %acilitate distillation generally. The mixture of steam and oil vapors passes out of the drum through the pipe 18 and is rectified in the column 20. The bottoms accumulating in the base of the column ordinarily consist of heavier lubricating oils and are conducted away through the pipe 50. A number of intermediate cuts are abstracted from the column through the pipes 33, 34, 35, 36 and 37. The amount of steam introduced through the pipes 28, 29, 30, 31 and 32 is so controlled as to strip these intermediate cuts to the desired extent and yield distillates of a predetermined flash. 0 The column is ordinarily operated under conditions of partial or substantially complete con densation provided by the cooling coils 40 and 41. Vacuum is maintained on the column 20 and connected apparatus by the joint operation of the jet ejector 56 and the barometric condensor 61. The method of opera-tion of these elements is substantially as follows:

The column is maintained under ,an absolute pressure of 50 mm. of mercury or less at the upper part thereof. This is maintained by the introduction of steam, preferably super-heated, through the pipe 57 which issues in the form of a number of jets from the orifices 57 a. The operation of these jets of steam at a high velocity serves to maintain the desired vacuum in the rectifying column. The amount of steam supplied to the jets is sufiicient to provide a pressure at the dis charge side of the ejector equivalent to about from 75 to 150 mm. of mercury absolute. A pressure within this range is maintained in the pipe 60 by the operation of the barometric condensor 61. The element 61 is of the cpnventional type and its construction andoperation need not be more fully described. In

the preferred method of operating the device, I adjust the amount of cooling liquid supplied to the pipes 40 and 41 so as to achieve substantially complete condensation of the oil vapors in the upper part of the rectifying column 20, while leaving the steam substantially uncondensed. The steam will, of course, carry a small quantity of hydrocarbon, but this should not, in an event, exceed more than 20% by volume of t e steam when operating with a crude oil residuum consisting principally of lubricating constituents such as, for example, a crude oil from which the gasoline, kerosene and gas-oil have been removed. In this way the column is operated to greater efficiency and capacity than would otherwise be possible and the combination of this method with that just described for maintaining a vacuum on the system results in a particularly economical and efiicient method of maintaining a relatively high vacuum and procuring excellent rectification with a minimum of cracking of the hydrocarbons.

It will of course be understood that the foregoing specific description of method and apparatus is by way of illustration and not of limitation. It is my intention that the invention be limited only by the appended claims or their equivalents in which I have endeavored to claim broadly all inherent novelty.

I claim:

1. The method of rectifying petroleum oils which comprises providing a column of rectifying zones under vacuum, admitting a mixture of petroleum oil vapors-and steam near the bottom of said column, condensing substantially all of the petroleum vapors at the top of said column by means of indirect heat exchange with a cooling medium, withdraw' ing substantially solely fixed gases and steam from the top of said column, and subsequently condensing said steam.

2. The method of rectifying petroleum oils which comprises providing a column of rectifying zones under vacuum in communication with each other, admitting a mixture of petroleum oil vapors and steam near the bottom of said column, passing a cooling medium in indirect heat exchange with the vapors at the top of said column, the temperature of the cooling medium being such as to condense substantially all of the petroleum oil vapors which reach the top of the column without condensing any substantial amount of steam, withdrawing substantially solely fixed gases and steam from the top of said column, and subsequently condensing said steam.

3. The method of rectifying petroleum oils which comprises providing a column of rectifying zones under vacuum in communication with each other, admitting a mixture of petroleum oil vapor and steam to said column so from the top of said co near the bottom thereof, passing a cooling medium in indirect heat exchange with the vapors at the top of said column to condense substantially all of the petroleum oil vapors thereat and leave substantially all of the steam thereat uncondensed, returning the condensed petroleum oil to the rectifying zones, withdrawing liquid petroleum distillates from a plurality of said zones, withdrawing substantially solely fixed gases and steam from the top of said column, and subsequently condensing said steam.

4. The method of rectifying petroleum oils which comprises progressively rectifying a mixture of petroleum vapor with added steam in a column of rectifying zones in countercurrent communication, partially condensing the mixture of vapors present in the upperrectifying zone by passing a cooling medium in indirect heat exchange with the said vapors, the amount of partial condensation bemg so controlled as to condense substantially all of the hydrocarbon components while leaving uncondensed substantially all of the steam, conducting away the steam at a rate sufficient to maintain the said column of rectifying zones under vacuum, returning the condensate to the rectifying zones, withdrawing petroleum distillates from a plurality of zones at intermediate points of said column of rectifying zones, withdrawing substantially solel xed gases and steam from the top of sai column, and subsequentl condensing said steam. I 5. The method of rectifying petroleum oils which comprises passing petroleum oil through a heater, vaporizing the oil while admixing steam therewith, passing the admixed vapors into the lower part of a column of rectifying zones in countercurrent communication maintained under vacuum, passing the petroleum oil in indirect heat exchange with the vapors in the upper part of said column before passing it through-the heater whereby substantially all of the petroleum oil vapors passing to the upper part of the said column are condensed and the petroleum oil is preheated in its passage to the heater, withdrawing substantially solely fixed gases and steam umn, and subsequently condensing said steam. In testimony whereof, I have signed my page to this specification this 5th day of July,

as PERCY c. mum, JR. 

